kutils (version 1.34)

reverse: Reverse the levels in a factor

Description

Simple literal reversal. Will stop with an error message if x is not a factor (or ordered) variable.

Usage

reverse(x, eol = c("Skip", "DNP"))

Arguments

x

a factor variable

eol

values to be kept at the end of the list

Value

a new factor variable with reversed values

Details

Sometimes people want to reverse some levels, excluding others and leaving them at the end of the list. The "eol" argument sets aside some levels and puts them at the end of the list of levels.

The use case for the eol argument is a factor with several missing value labels, as appears in SPSS. With up to 18 different missing codes, we want to leave them at the end. In the case for which this was designed, the researcher did not want to designate those values as missing before inspecting the pattern of observed values.

Examples

# NOT RUN {
## Consider alphabetication of upper and lower
x <- factor(c("a", "b", "c", "C", "a", "c"))
levels(x)
xr1 <- reverse(x)
xr1
## Keep "C" at end of list, after reverse others
xr2 <- reverse(x, eol = "C")
xr2
y <- ordered(x, levels = c("a", "b", "c", "C"))
yr1 <- reverse(y)
class(yr1)[1] == "ordered"
yr1
## Hmm. end of list amounts to being "maximal".
## Unintended side-effect, but interesting.
yr2 <- reverse(y, eol = "C")
yr2
# }